The present invention relates to an image forming apparatus such as a printer, a copier or the like using electrophotographic technique.
In an electrophotographic technique used in an image forming apparatus such as a printer, a copier or the like, an exposing device irradiates a photosensitive drum (as an image bearing body) with light so as to form a latent image according to inputted image data, and a developing device develops the latent image using a toner (as a developer) to form a toner image. The toner image is transferred to a sheet (as a recording medium), and then is fixed to the sheet.
Generally, the developing device includes a developing roller that supplies the toner to the photosensitive drum, a supplying roller that supplies the toner to the developing roller, a regulating blade that regulates a thickness of the toner layer on the developing roller. The toner is supplied by a detachable toner cartridge, and is charged by friction at a contact portion between the developing roller and the supplying roller and at a contact portion between the developing roller and the regulating blade according to a developing voltage and a supplying voltage respectively applied to the developing roller and the supplying roller.
In the image forming apparatus using such a developing device, it is desired to prevent a blurring of the toner image and a smear caused by adhesion of the toner due to time-dependent changes and environmental changes. For this purpose, the developing voltage and the supplying voltage are controlled based on a density of a density correction pattern formed on a transfer belt and a density of the image data to be printed (see, for example, Japanese Laid-Open Patent Publication No. 2004-29681).
Recently, there is a demand for an image forming apparatus capable of forming excellent images.